The Arizona senator sent the third in a series of letters to Gen. Keith Alexander trying to explain why DoD, not DHS, should be in charge of defending critical infrastructure from cyber attacks. He said the administration's approach would create another layer of bureaucracy and slow down responses to threats.

Asserting that cyberattacks against the U.S. don't come only from China, the U.S. and Chinese defense ministers said they agreed Monday to work together on cyber issues to avoid miscalculations that could lead to future crises.